Microwave switching device having moveable jumper for internally shorting electrodes of t-r tube



m 1 R. L. HUBBELL ET AL 3,092,791

MICROWAVE swncnms DEVICE HAVING MOVEABLE JUMPER FOR INTERNALLY SHORTING ELECTRODES OF T-R TUBE F'iled March 8. 1961 INVENTORS RICHARD L. HUBBELL FRANK A. RECORD FIGZ ATTO R N EY United States Patent MICROWAVE SWITCHING DEVICE HAVING MOVEABLE JUNIPER FOR INTERNALLY SHORTING ELECTRODES 0F T-R TUBE Richard L. Hubbell, Arlington, and Frank A. Record, Danvers, Mass., assignors, by mesne assignments, to Varian Associates, Palo Alto, Calif., a corporation of California Filed Mar. 8, 1961, Ser. No. 94,297 Claims. (Cl. 33313) The present invention relates generally to microwave frequency gaseous discharge switching devices with integral protective mechanism and, more specifically, to a novel and improved mechanism for attenuation of undesirable microwave frequency signals.

Prior art switching devices incorporated in radio direction and ranging systems are coupled between the common antenna and the sensitive receiver. A specific group of such devices is commonly referred to as transmitreceive 01' TR tubes. An internal highly ionized gaseous discharge within a metallic or dielectric envelope is initiated upon exposure to high power pulses transmitted to the common antenna. The reflected returning pulses at a lower power level pass through the TR tube without *a discharge to the receiver. It is necessary to protect the sensitive elements within the receiver during non operation of the TR tube when a discharge cannot be initiated. An attenuating protective mechanism has been incorporated in the TR tube. This mechanism is referred to as a shutter in accordance with US. Patent 2,734,171, issued February 7, 1956 to Harold Heins and assigned to the iassignee of the present invention. The mechanism disclosed provides a metallic shorting member within a resonant element of the TR tube and is electromechanically controlled. When the TR tube is inoperative, the shorting member extends across the Waveguide path to contact another resonant element and thereby attenuate any undesired signals.

In accordance with advancements in the art, generators of very high frequency signals have become available. At these frequencies waveguide dimensions are extremely small and the aforementioned attenuating mechanisms cannot be employed. An example may be the to 17 kilomegacycle frequency range where the broad Waveguide wall is .702 inch and the narrow wall is .391 inch. Since generators have now been developed up to 75 kilomegacycles, a need exists for a protective attenuating mechanism for TR switching devices at such high frequencies of transmission.

Accordingly, it is an object of the present invention to provide a gaseous discharge switching device having a new and novel protective attenuating mechanism.

In accordance with the present invention, a gas switching TR tube having conventional internal resonant elements is provided with metallic means extending parallel to the envelope broad walls. Movement of the metallic means by conventional electromechanical means results in simultaneous short circuiting of a plurality of resonant elements to attenuate by a value of 40 db or better any signals entering the tube. A feature of the invention resides in the provision of a new and novel means for protecting a sensitive receiver in TR switching tubes having small internal dimensions. An additional feature is the shorting of multiple resonant discharge gaps with single electromechanical means at a saving in cost, as well as, :a reduction in number of external structures disclosed in the aforementioned patent.

Further objects, features and advantages will become apparent after consideration of the following detailed specification and appended drawing, in which:

FIG. 1 is a perspective view of the embodiment of the invention with a portion of the tube envelope broken away to reveal internal structure;

FIG. 2 is an enlarged detailed view of the embodiment shown in FIG. 1 along the line 2-2.

Referring now to the drawing, the illustrative embodiment is a broad band TR switching tube comprising a sec tion of rectangular waveguide 1 defining parallel broad walls 2 and narrow walls 3. Secured adjacent the ends are conventional mating flanges 4 and 5. A resonant window assembly 6 encloses each end of the waveguide section to thereby provide a hermetically sealed envelope. Each window assembly includes a dielectric member pervious to microwave energy signals. The envelope contains a gaseous ionizable atmosphere under reduced pressure to provide a highly intense gaseous discharge when high power microwave frequency energy is transmitted to the window assembly positioned within flange 4.

Disposed transversely within the waveguide envelope at intervals of a quarter of a wavelength are a plurality of resonant elements. Included are a plurality of paired metallic plate members 7 defining irises 8. Disposed within each iris are spaced oppositely disposed conical electrodes 9, 10, 11, 12 defining discharge gaps 13 and 14, having axes taken in the direction of a discharge across the gaps. An ignitor electrode 15 having a metallic probe 16 and dielectric bead 17 is supported by a collar 18 with the inner end 19 of the probe exposed to the inside of the envelope adjacent one of the plate members 7. An ioniza'ble gaseous atmosphere of a suitable gas such as helium, argon or hydrogen with a small percentage of water vapor is provided within the envelope at a reduced pressure of a few millimeters of mercury.

Pursuant to the teachings of the present invention, the novel attenuating mechanism is introduced into the tube envelope through one of the narrow walls 3. The mechanism comprises an elongated shorting bar member 20 supported by a drive rod 21. A desirable material may be 'berrylium copper or other metals having a resiliency for good contact and a slight flex-ing or bowing is preferred. FIG. 1 illustrates the mechanism in the open position with the discharge gaps 13 and 14 uninhibited for normal TR switch operation. The member 20 is touching the face of the plate iris members 7 and is the end limit of travel toward the adjacent narrow waveguide wall 3.

FIG. 2 illustrates the closed position when the TR switch tube is inoperative. The shorting bar member 29 contacts both pairs of conical electrodes to thereby effectively short circuit the electrodes and attenuate any undesired signals entering the tube envelope. The bar 29 moves into the gaps 13 and 14 from a direction transverse to the axes of the gaps. To facilitate seating of the bar member against the convergent end of all the conical electrodes, a notch 22, visible in FIG. 1, may be desirable.

The attenuating mechanism is activated by electromechanical means 23 secured to the narrow waveguide wall 3 by a collar member 24. A metallic core 25 of soft iron having an axial bore 26 houses an end of the rod 21. An electrical coil 27 surrounds core 25 and is connected to an appropriate voltage supply, such as 14 or 28 volts DC. by means of terminals 23 mounted on an insulator 29 with wires 30 extending from the coil. The housing 31 encloses the aforementioned components. Armature 32 of a suitable material secured to rod 21 is urged forward by spring 33 and upon energizing of the electromechanical means the tension of the spring is overcome to move the shorting member 29 to the open position. To avert dislocation of the armature 32 in moving between the open or closed positions, an anchor pin 34 may be provided extending through an aperture in the armature.

In an experimental embodiment for use at a frequency wherein the dimensions necessitate conical electrodes having a tip-of .015 inch or less, attenuations of 40 db or better were achieved. In the open position, the shorting bar member appears to have a negligible effect on insertion loss since the overall tube measured only .5 db insertion loss.

Hence, while prior art protective mechanisms require separate short circuiting means for each discharge gap, there is disclosed a single means forachieving this purpose for a plurality of gaps. Further, a single electromechanical means will now activate an attenuating mechanism for protection of switching tubes from undesired microwave frequency signals.

While a specific illustrative embodiment has been described above, it is intended that all matter appearing herein and shown in the drawing be interpreted in a broad sense consonant with the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A microwave switching device comprising a metallic envelope filled with-an ionizable atmosphere under re- .duced pressure, resonant elements including plural opposed conical electrode structures spaced within said envelope to define plural discharge gaps having axes in the direction of the discharge across :the gaps, attenuating means including a metallic shorting bar member adapted to simultaneously contact a plurality of said electrode structure by moving into the gap from a direction trans verse to the axes of said gaps, and electromechanical means to control movement of said shorting bar member.

2. A microwave switching device comprising a rectangular waveguide envelope having parallel brood and narrow walls and containing an ionizable atmosphere under reduced pressure, plural spaced resonant conical electrodes having opposed convergent ends extending firom opposite broad walls to define plural discharge gaps, attenuating means including an elongatedmmetallic shorting .bar member adapted to simultaneously contact all the electrode ends and being movable in a-plane approximately parallel to the bro-ad side walla-and electromechanical means mounted on one of saidnarrow'walls to control-movement of said shorting bar member.

3. A microwave switching-device according to claim 2 wherein said shorting, bar member-is fabricated with a bowed configuration.

4. A microwave switching device a'ccording-to claim 2 wherein said electrode ends are provided with means adapted to facilitate seating of theshorting bar member upon contact therewith.

5. A microwave switching device comprising, an envelope filled with an i-onizable atmosphere-under reduced pressure, a resonant element disposed within said envelope to define a discharge gap, said discharge gap having van axis taken in the direction of the discharge across the gap, attenuating means for short circuiting said discharge gap by moving into the gap, from a direction approximately transverse to the axis of said discharge gap, and an electro mechanical means cooperating with and controlling the movement of said attenuating means.

References Cited inthe file of this patent UNITED STATES PATENTS Heins Feb. 7, 1956 Braden Dec. 10, 1957 OTHER REFERENCES 

1. A MICROWAVE SWITCHING DEVICE COMPRISING A METALLIC ENVELOPE FILLED WITH AN IONIZABLE ATMOSPHERE UNDER REDUCED PRESSURE, RESONANT ELEMENTS INCLUDING PLURAL OPPOSED CONICAL ELECTRODE STRUCTURES SPACED WITHIN SAID ENVELOPE TO DEFINE PLURAL DISCHARGE GAPS HAVING AXES IN THE DIRECTION OF THE DISCHARGE ACROSS THE GAPS, ATTENUATING MEANS INCLUDING A METALLIC SHORTING BAR MEMBER ADAPTED TO SIMULTANEOUSLY CONTACT A PLURALITY OF SAID ELECTRODE STRUCTURES BY MOVING INTO THE GAP FROM A DIRECTION TRANSVERSE TO THE AXES OF SAID GAPS, AND ELECTROMECHANICAL MEANS TO CONTROL MOVEMENT OF SAID SHORTING BAR MEMBER. 